It is on the market now, the price is pretty good, if it is the same as Shapton glass you are basically getting a double thick version with half the price
I wouldn't think the glass part of the GS is nearly as expensive doubling the abrasive portion. My guess is this is an attempt by Shapton to entice Japanese buyers to buy into their resinoid stone line, by proposing a more familiar form factor (i.e no glass backing), and an abrasive thickness less radically reduced from what Japanese buyers were accustomed to.@Tekkz , we'll only know for sure if you buy one!
I'm curious, so i sent Miura (and also Shapton) an email asking if it was "identical material". Will post reply. If it is, it's interesting they'd double the material in exchange for the glass, and offer that at a lesser price, as the Glass series has such huge market share already. Perhaps the glass+ mounting process is costly, and changing allows for a better profit margin??? All speculation on my part. Will post their response.